facebook/relay · error

Failed to spawn daemon process

Error message

Failed to spawn daemon process

What it means

Startup panic in start_daemon_process: Command::spawn failed when trying to launch the compiler server as a background child process (current exe re-invoked with the 'server ... start --foreground' argument vector). Spawn failures are environmental — executable permissions, fd limits, or resource exhaustion — not compilation errors.

Source

Thrown at compiler/crates/relay-compiler/src/server_daemon.rs:397

    args.extend(start_extra_args.iter().cloned());

    let log_path = get_log_file_path(config_path, projects);
    let log_file = File::options()
        .create(true)
        .append(true)
        .open(&log_path)
        .expect("Failed to open daemon log file");
    let log_file_clone = log_file
        .try_clone()
        .expect("Failed to clone daemon log file handle");

    let mut child = Command::new(current_exe)
        .args(&args)
        .stdin(Stdio::null())
        .stdout(Stdio::from(log_file))
        .stderr(Stdio::from(log_file_clone))
        .spawn()
        .expect("Failed to spawn daemon process");

    let socket_path = get_socket_path(config_path, projects);
    let max_attempts = 60;
    for i in 0..max_attempts {
        tokio::time::sleep(std::time::Duration::from_secs(1)).await;

        // Detect early daemon-process exit (e.g. invalid project name).
        if let Some(status) = child
            .try_wait()
            .expect("Failed to check daemon process status")
        {
            error!("Daemon process exited during startup with {status}");
            log_daemon_file(&log_path);
            std::process::exit(1);
        }

        if send_request(&socket_path, DaemonRequest::Version)
            .await

View on GitHub (pinned to 668b1b85e0)

Solutions

1. Verify the current executable is still present and executable (it may have been replaced mid-run by a rebuild)
2. Raise process/fd limits if the system refuses to fork or allocate stdio pipes
3. Check overall system memory and process counts; retry after freeing resources

When it happens

Trigger: Thrown at compiler/crates/relay-compiler/src/server_daemon.rs:397 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of facebook/relay@668b1b85e0 (2026-09-02). Data as JSON: /api/errors/9969b7ef5e78d04c. Report an issue: GitHub.